Blue Green Algae Alert


Blue-green algae [By Pseudopanax via Wikimedia Commons]

Press release from Humboldt County Department of Health and Human Services:

Local Public and Environmental Health officials are warning recreational users of all bodies of fresh water to avoid contact with cyanobacteria (also known as blue-green algae).

The North Coast Regional Water Quality Control Board in cooperation with the Humboldt County Department of Health & Human Services, Mendocino County Environmental Health and Lake County Public Health Division issued a warning to avoid contact with cyanobacteria and algal blooms. Although commonly referred to as blue-green algae, following the lead of the state, jurisdictions are using the term cyanobacteria as it is not algae, but bacteria.

Typically, cyanobacteria warnings come out between late July and early August, coinciding with low flows and sustained high temperatures in the inland areas which may contribute to cyanobacteria growth in the river.

Human activities have an effect on nutrient and water flows in rivers, streams and lakes. Nutrients found in fertilizers, animal waste and human waste can stimulate blooms. Excessive water diversions can also increase water temperatures and reduce flows. People can take the following measures to prevent algal blooms in our waters:

  • Be conservative with the use of water, fertilizers and pesticides on your lawn, garden or agricultural operation.
  • Avoid nutrient runoff by recycling any “spent” soil by tilling it back into gardens, or protecting it from rainfall.
  • Create shade and filter out nutrients by planting or maintaining native plants around river banks.
  • Inspect and pump out septic systems every three to four years.
  • Prevent surface water runoff from agricultural and livestock areas.
  • Prevent erosion around construction and logging operations.

Cyanobacteria can be present in any fresh water body. It looks like dark green, blue-green, black, orange or brown scum, foam or mats on the riverbed or floating on the water. Warm water and abundant nutrients can cause cyanobacteria to grow more rapidly than usual causing “blooms.” These blooms are termed “harmful algal blooms.” Most cyanobacteria does not affect animals or people, however, a small number of cyanobacteria species are capable of producing toxins that can be harmful to animals and humans. Dogs and children are most likely to be affected because of their smaller body size and tendency to stay in the water for longer periods of time.

The presence of cyanobacteria has been previously confirmed in some water bodies within Humboldt, Mendocino and Lake counties including the South Fork Eel River, Van Duzen River, Trinity River, Clear Lake and Lake Pillsbury. It is difficult to test and monitor the many lakes and miles of our local rivers. Most blooms in California contain harmless green algae, but it is important to stay safe and avoid contact.

Officials recommend the following guidelines for recreational users of freshwater areas:

  • Keep children, pets and livestock from swimming in or drinking water containing algal scums or mats.
  • Adults should also avoid wading and swimming in water containing algal blooms. Try not to swallow or inhale water spray in an algal bloom area.
  • If no algal scums or mats are visible, you should still carefully watch young children and warn them not to swallow any water.
  • Fish should be consumed only after removing the guts and liver and rinsing fillets in tap water.
  • Never drink, cook with or wash dishes with water from rivers, streams or lakes.
  • Get medical attention immediately if you think that you, your pet, or livestock might have been poisoned by cyanobacteria toxins. Be sure to tell the doctor or veterinarian about possible contact with cyanobacteria or algal blooms.
  • Join or support one of the many watershed and river organizations.

To learn more about cyanobacteria and harmful algal blooms, visit the state of California’s website at

To learn more about cyanobacteria and algae on the South Fork Eel River, visit

To report a bloom, e-mail or call 844-729-6466 (toll free). Blooms can also be reported via the “bloomWatch” app which is available for free download on iTunes or Google play.

For information on conditions occurring within Humboldt County, contact the Division of Environmental Health at 707-445-6215 or 800-963-9241. Photos of suspected blooms can also be emailed to


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  • So where can we swim?

  • Mattole wasnt on that list. Thats where ill be going for the rest of the summer.

  • Go to Trinity to swim.
    Or if u know a local in so hum ask them to take you to the spots that usually have less algae this time of year. Im not giving up the locales here except for one thats a campground, standish hickey which has a good hole. If you go please stop at the peg house and give them some business 🙂

  • unbridled philistine

    Cannot blame the areas Wastewater treatment plants around here they all go to the fields with their effluent this time of year.. Growers and all that fertilizer 10-10-10… High off.

    • how do you blame runoff if it is the dry season? high water flats adjacent to the river would be a better term than fields. and what kind of sediment is below the surface of these flats? this is no different than the problem at Clam beach. but I wonder how the North Fork Smith above Major Moore’s in Oregon also has this blue green problem? no grows, no septic tanks and the only human influence is a few dozen people that camp at sourdough each year. The entire watershed is wilderness. I blame the water temp, the north fork has been studied for years and some of the temp meters hit 22-23 degrees C late in the year.

    • Runoff controls ph. Cyanobacteria only grows at ph 9-11. Algae no at that ph.change fertilizer seller.i don’t know ph change from using inland sea phytoplankton. But this incredible pot money is so ignorantly poisoning the whales and their peers.inland sea plankton is complete element feed for vitamin synthesis etc.runoff that could help sea life.imagine a food chain based on ammonia based fertilizers and pot rich people operating the valves.doctors to one side distributing opiates.depressing.

  • My newphew took his momma dog and her pups to the van duzen river on a hot day a few years ago, and by morning she was dead as we’re all the puppies except one.
    Vet confirmed it was the algae.
    This stuff is serious.

  • I hope all those festival promoters warn and educate all those 8,000 to 10,000 people per day for Northern Nights, Reggae on the River and The Redwood Run. It just seems they are adding to the problem.

    I also hope the Garberville Sanitary District gets their new chlorine contact chamber up and running soon, since the old one took a dump, they cannot treat the water properly without having to add twice or three times the amount of chlorine to make the water safe to drink. Hope no one gets sick.

  • The Big Valley and Elem EPA Depts. have been carefully sampling several areas around Clear Lake for years. No other agency has been as diligent. See/bookmark:

    Get the latest info- sampling on Facebook:

    photo is a recent sample: Dolichospermum cyanobacteria, Elem’s shoreline.

    Knowledge is power.

  • This photo was taken last summer, near Konocti Harbor area of Clear Lake
    Credit: Phil Kleyn Schoorel

    • And since Clear Lake is a natural lake, not man made, its been the man made development and sewer septic systems that have increased just since WWII. Here is one great example of a man made development and subdivision in Clear Lake Oaks:,-122.669573,1422m/data=!3m1!1e3?hl=en-US

      Even though Clear Lake has its own inherent naturally occurring effects to the water quality and aquatic species; it never ceases to amaze me how non-indigenous people think they can change the whole eco-system by spraying and trying to kill what they don’t like to see or smell and think is bad for the lake…

  • I’ve watched the forestry fire trucks pull down to the van duzen and pull water straight out of the river. Twice a day. For the four days we swam there. Right next to us swimming. Kind of bothered me. But, they probably can do that legally. Idk

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